The invention provides new solutions to address certain major environmental problems typically encountered in hydrocarbon exploration and production wells, especially in offshore operations. A common practice in certain regions (for example the Middle East) is to stimulate drain holes in carbonate reservoirs with hydrochloric acid, and then clean up the well before connecting it to the production line. One previous approach has been to direct clean up fluids through a burner until the pH falls to less than 6, burning all hydrocarbons produced and dumping the spent acid and contaminated mud in the sea Burning has an environmental and economical impact. The hydrocarbon burning produces toxic gases, soot, acid rain, unburned hydrocarbons and a large amount of CO2, all of which are detrimental to the environment.
The direct economic impact is the cost of the oil and gas lost in flaring as well as the cost of burning equipment. This equipment has a large footprint (physical size), cost, power consumption and noise. Moreover, the risk of acid corrosion of pipelines under the sea is high. Any pipeline leak resulting from corrosion can potentially cause a shut down of production for several weeks as well as high repair costs and major pollution. Indirect costs linked to the large liability exposure due to the potential and actual damage to the environment are difficult to evaluate but could be several order of magnitude larger than direct costs.
In addition to acid and mud, well fluids, often containing oil at a concentration of about 3000 ppm, are also often dumped into the sea One aim of the present invention is to provide techniques to help reduce the oil content of water from a typical 3000 ppm to 10–80 ppm during a well test operation.